Not all water supplies have the same quality water due to variations in its mineral composition. In certain regions water may produce bad odors, such as a rotten-egg smell due to certain types of bacterial produced by sulphur contained therein. Such water is known as hard water which emanates from underground where it is in contact with in all sorts of minerals. Such rotten-egg smell water when heated in a water heater is amplified. In an attempt to resolve this problem different aluminum sacrificial anode compositions have been developed wherein a certain percentage of zinc is introduced in the alloy. Sacrificial anodes are utilized in water heaters for cathodic corrosion protection of the cathode and which cathode consists of any exposed steel in a flawed glass-lined tank. The glass lining secured on the inside wall of the tank is to isolate the steel from the water and thereby increase the life span of the water heater. However, any flaws in the glass lining and about fittings exposes steel to the water and this causes electrolysis, a current flow, between the anode and the cathode and deterioration of the sacrificial anode. The intensity of the current flow amplifies the bad odor of the water.
In an attempt to protect the steel tank from corrosion and reduce the bad odors generated by such hard water, an aluminum-zinc alloy material was utilized as the anode for replacement of the commonly used magnesium anode. This offered some protection against certain bacteria contained in the water. The alloy composition contained zinc and trace metals, such as tin, iron and silicon and the balance aluminum. However, these replacement anodes, during electrolytic reaction, produced more hydrogen at the exposed steel surfaces than the magnesium anode when active. It was concluded that the higher production of hydrogen when combined with sulphur in hot water, accelerated the bad odors generated by the bacteria, particularly when the anode had been greatly consumed. Because such anode also deteriorated more quickly, there was a need for replacement after about four years of service which, of course, is dot desirable and such also added to cost to the consumer. It has also been expressed in the literature, that aluminum can be a health hazard when exposed to drinking water. Accordingly, if hot water from a water heater containing an aluminum alloy anode is often utilized as drinking water, for example in admixture with instant coffee etc., it could create a health hazard in long term. Powered anodes is said to be a preferred solution to the use of aluminum anodes. Another solution is to treat the water with chlorine before it enters the tank, but this is an expensive solution.